Excess dietary intake is a principal modifiable risk factor for the leading causes of morbidity, mortality, and health care expenditures in the United States. Obesity and poor diet are strong risk factors for heart disease, stroke, and diabetes, and together account for nearly one-quarter of total mortality in the U.S. population. Together, dietary factors and obesity account for about 23% of total mortality in the U.S. population. One-third of the adult population is obese, and three-quarters do not meet dietary guidelines for saturated fat, sugar, sodium, fruit, or vegetable intake.
The prevalence of obesity is projected to increase dramatically among U.S. adults from the current level of about 29% to about 42% by 2030, which would have a devastating impact on health burden and the healthcare system. By preventing this projected increase in the prevalence of obesity, the United States could avoid about 6.8 million cases of heart disease and stroke, about 8 million cases of diabetes, and about 0.5 million cases of cancer, and save over $550 billion in obesity-attributable health care costs.
One of the most profound changes to the food environment has been an increase in the availability of extremely palatable, high-calorie, nutrient poor snack foods. As a result, snacking has become more frequent among both adults and children since the 1970's, and snacks have increased in both portion size and calorie content. For adults, calories from snacks have increased by about 240 calories per day, and now account for about 24% of total energy intake.
Vending machines are the most prevalent source of high-calorie snacks in the United States. There are about 1.32 million snack vending machines across the United States, or about 1 for every 180 adults. Most snack machine purchases are unhealthy; all of the 20 top-selling vending machine snacks between 2008-2011 were chocolate or non-chocolate candies, pastries, or full-fat chips.
Worksites, school systems, and other organizations have attempted to reduce consumption of high-calorie vending machine snacks by removing these items from their machines, or removing the machines altogether. However, restriction-based strategies are not financially feasible for most organizations, and ignore the fact that vending machines can be an important food source in settings such as night shift work and rural worksites.
In response to rapidly growing demand for healthier vending options in schools, city governments (including Chicago), and worksites, snack machines are increasingly being stocked with healthier snack products. Organizations have put healthier options in snack machines, but they are not being consumed. There is a need for effective strategies that shift individuals' choices toward these healthier options. Strategies that improve the healthfulness of snack vending machine purchases could reach millions of individuals on a daily basis. Reducing average calorie intake by as little as about 40 calories per day (approximately 15% of a typical vending machine snack) would halt the obesity epidemic and prevent obesity in approximately 90% of the next generation of Americans. Simulation studies based on the dynamics of body weight regulation suggest that reducing calorie intake by about 40 calories per day (range: about 7-100 calories) would prevent obesity in about 90% of the next generation of Americans. This level of change represents about 15% of a typical vending machine snack, and is well within the potential range of improvement that could be achieved through vending machine interventions.
Prior vending machine interventions have focused on modifying the availability or price of healthy and unhealthy snack products. Some proposals have called for removal of unhealthy snacks from vending machines, or complete removal of vending machines altogether, particularly in school settings. However, restriction-based strategies have a major negative impact on vending revenue, which makes restriction infeasible for most organizations from an economic standpoint. As a result, snack vending machines are present in about 87% of middle schools and about 98% of high schools. Restriction based strategies involve removing snack options, rather than shifting choices to healthier options, which may lead to reliance on alternative sources of unhealthy snacks. Restriction-based strategies also overlook the fact that healthy snacks provide important nutrients and can promote weight control, and that vending machines are an important source of snacks in some key settings.
In contrast to restriction, pricing interventions have a reliable influence on food choice, both in general and in vending machines specifically. In prior studies price reductions for low-fat foods produced a dose-dependent increase in purchasing rates for these items, with low-fat purchases increasing from about 11% to about 21% of sales under about 50% price reductions. Similarly, a differential pricing intervention on the Rush University Medical Center campus showed that an about 25% relative price difference increased vending machine sales of healthy snacks from about 19% to about 46% of total sales. Importantly, neither pricing intervention harmed overall vending revenue, which is important for the feasibility of disseminating pricing interventions in the real-world. Pricing interventions are effective, but have several significant limitations, including that they are “regressive” (disproportionately affect low-income individuals) and that sweet snacks are less responsive to pricing interventions than most other types of foods. Additionally, both restriction- and pricing-based interventions have failed to obtain public support; a recent national survey found that about 74% of Americans opposed public health obesity interventions that limit consumer choice, and about 59% opposed taxes on unhealthy foods.
Thus, there remains a significant need to identify strategies that can augment or substitute for pricing interventions in order to improve the healthfulness of snack machine choices.